Radiant energy transmission and reflection analyzer with adjustable filter



Z50-201 ^U 252 EX gROSS REFERENCE EXAMNER FIPBZIZ XR 21589141# March 18, 1952 E. .1. MARTIN ETAL 2,589,414

RADIANT ENERGY TRANSMISSION AN-"l REFLECTION ANALYZER WITH ADJUSTABLE FILTER Y Filed Sept. 23, 1947 4 Sheets-Sheet l CROSS REFERENCE l- Mwuwnn March 18,1952 E. J. MARTIN ETAL 2,589,414

RADIANT ENERGY TRANSMISSION AND BEFLECTION ANALYZER WITH ADJUSTABLE FILTER Filed Sept. 23, 1947 4 Sheets-Sheet 2 March 18, 1952 E. J. MARTIN ETAL RADIANT ENERGY TRANSMISSION AND REELEcTIoN ANALYzER WITH ADJUSTABLE FILTER Filed Sept. 23, 1947 4 Sheets-Sheet 25 Cvf Bnventora MQW Gttornegs a (Z M .w

4 Sheets-Sheet 4 RADIANT ENERGY TRANSMISSION AND REFLECTION ANALYZEIR WITH ADJUSTABLE FILTER Marchl '418; 1952 Flled Sept 25 1947 Patented Mar. 18, 1952 RADIANT ENERGY TRANSMISSION AND RE- FLEC'EIION ANALYZER WITH ADJUSTABLE FILT R Edward John Martin, Pleasant Ridge, Mich., and Robert N. Frawley, El Monte, Calif., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application September 23, 1947, Serial No. 775,666

, se e mw-...elven e i claims. 1

The present invention 'relates to a radiant energy transmission and reflection comparison apparatus. More particularly it relates to a radiant energy transmission and reflection analyzer of the type in which a standard material is compared with a test specimen using an adjustable neutral lter.

Previous to the present invention the necessity of taking a large number of readings independently both through a standard material and the test material and mathematically correlating the results of these various readings has made transmission and reflection analysis quite complicated and diflicult. The present invention makes possible the automatic comparison of the energy transmission, or re.- ecton of, a standard material, or surface, and the specimen under test. The present invention utilizes a variable neutral filter interposed between the source of radiation, and the standard material or specimen under test (depending on which has the greater transmission or reflection coeicient). The energy source, test specimen, standard material, variable iilter and radiation receiver are so arranged that the energy is first radiated through the standard material and then through the test specimen, the received energy is compared, the variable iilter placed between the energy source and either the standard material or specimen under test and adjusted by means of a servo mechanism so that the energy received is substantially constant at all times. The lter adjustment may be calibrated to indicate the relative transmission or reilection of the specimens.

It is therefore an object oi' the present invention to provide a simple and efiicient means for comparing energy transmission and/or reflectivity.

It is a further object of the present invention to provide a neutral, adjustable, raster or filter.

It is a still further object of the present invention to provide a transmission and reection analyzer in which the energy source is first concentrated on one material and then on a second material plus a neutral lter and the received energy analyzed so as to determine the relative transmission or reflection of the materials.

It is a still further object of this invention to provide a simple, eiicient and accurate infrared ray spectrograph.

Other objects of this invention will become apparent upon reading the specification and inspection of the drawings and will be particularly pointed outin the claims.

Referring to the figures in the drawings:

Figure 1 is a schematic diagram of one modiiication of the present invention.

Figure 2 is a cross section of the optical system of Figure 1 taken 90 to the plane shown in Figure 1.

Figure 3 is a schematic showing of the present invention used to compare reflectivity.

Figure 4 is a plan view of the controllable filter or raster with the associated mechanism for oscillating the specimens and filter.

Figure 5 is a more detailed view of the controllable filter and oscillating mechanism.

Figure 6 is a partial sectional view taken along the line 6-6 of Figure 4.

Figure '7 is a plan view showing the method of mounting the standard and the test specimens.

Figure 8 is a sectional view along line 8-8 of Figure 7.

Figure 9 illustrates a means of oscillating the standard and test specimens radially to the raster or lter.

Figure 10 shows the means of oscillating the test specimen and standard material tangential to the raster or filter.

Figure 11 shows a modification of the illter.

Figure 12 is an elevational view of Figure 1l.

Figure 13 is a partial sectional view taken along the line l3--I3 of Figure 11.

Referring more particularly to Figures 1 and 2. the source of energy radiation 2 is illustrated as a line source. The energy from this source is projected along the direction 4 to the spherical convex lens 6. This lens projects the energy along the lines 8 through the slit I0 in the analyzer. The energy after passing through the slit lll is projected on to the radiation receiver l2 by means of a second lens I4. A neutral filter IE of known and adjustable density, plus a cell A I8 containing a test specimen 20 and a standard specimen 22 of known transmission characteristics, is interposed between the lens 6 and the slit I0 in the energy analyzer. The iilter I6 plus the cell I8 is oscillated transversely of the slit iD so as to compare the energy transmission through that slit. As illustrated in the modincation of the present invention shown in Figures 4, 5 and 6, the neutral iilter is a rotating disk with controllable segmental openings. This filter is adjusted by means of control motor 24 in such 4a manner that when in balance the energy received by the radiation receiver l2 is substantially constant. It is desirable but not necessary that the conguration of the cell I8 containing the test vspecimen andstandard be such and its movement so correlated that the energy received by the receiver I2 will approximate a sine wave. The energy received by this receiver will, of course, be constant when the system has been completely balanced by the proper adjustment of the lter I6 by the motor 24. In order to obtain this proper adjustment the energy received by the radiation receiver is transformed by the receiver into electrical energy and transmitted to the control unit 26 by means of wires 28 and 38. This control unit 26 contains the proper amplifier, phase diierentiator and control circuits to energize and cause motivation of the control motor 24 when the energy received by the radiation receiver I2 is oscillating. The armature of this control motor 24 is thereby rotated and adjusts the filter I6 to such a point that the energy received by the radiation receiver I2 is constant. It may be found desirable to drive an indicating or recording instrument 288 to automatically determine or record the degree of transmission of the lter and thus indicate or record the transmission ratio between the standard and test specimen at any and all desired frequencies within the range for which the system is designed to operate.

Figure 3 shows the present invention used to compare reectivity of a standard coating 32, and a test coating 34 on a cell 36. In this modication of the invention the source 2, the lens 6, the slit I8, lthe lens I4, and the radiation receiver I2 may be the same as, or similar to those used in the modication of this invention shown in Figures 1 and 2. In order, however, to obtain the proper control and concentration of the rays of energy an additional optical system including lens 38 must be interposed between the cell 36 and the lter 48. The lter 48 in this modifica? tion of the invention may be of the same general type as that shown in Figure 1 and may be controlled in the same general manner. In this modification, however, the cell and filter must be oscillated in phase but depending on the optical system used, they may or may not be actuated in the same plane. This modification of the present invention is very useful in the comparison of various coating colors and degrees of polish. This modification, for example, is useful in matching paints or other finishes. It is also very useful in comparing the condition of polish, or degree of roughness, of a nished surface.

Referring to Figure 4, the variable lter I6 is illustrated as containing a series of metallic or other opaque disks having openings therein and so arranged with each other that these openings register to permit the transmission of light in variable amounts up to '75 per cent complete transmission, while the entire system of plates is rotated at high speed. The speed of rotation of these plates and hence the rapidity at which the light through the cell is changed must be very great as compared to the speed at which the cell is shifted in front of the slit in the analyzer. 'I'his is necessary in order that any pulsation in energy caused by the segments may be easily nltered by the radiation receiver and/or control unit. The entire raster unit, including the rotating nlter and also the cell I8, is oscillated in front of the slit of the analyzer by reciprocating the assembly including these members by means of a crank and connecting rod assembly. A motor 48 is connected to the crank 42 by means of couplings 44 and 46 and gear box 48. This crank 42 which is directly connected to the coupling 46, is connected to the plate 58 by means of connecting rod 52 and crosshead pin 54.

Referring to Figure 5, the plate 58 is reciprocated in guide 5I carrying the entire assembly with it. As the assembly is reciprocated, a motor 56 rotates the filter disks IIB at high speed.

Referring to both Figures 5 and 6, the motor 56 is connected to a shaft 58 having splines 68 and 62 thereon. The splines 68 carry a spiral gear 64. This spiral gear 64 has freedom of axial movement on the splines 60 and is adjusted at the desired axial location by means of carrier 66. The spline gear 64 drives a mating gear 68 on a small jack shaft 18. This spiral gear 68 is rigidly attached to the shaft 'I8 as is also the spur gear '12. The shaft 58 also has mounted thereon a tubular member 14 having freedom of rotary movement with regard to said shaft 58 but mounted in a fixed axial position by collar 16. Rigidly mounted on the tubular member 14 by means of a set screw 18 is a spur gear 88 so positioned as to mate with spur gear l2 on jack shaft 18. The pitch diameter of the `gears 68 and 12 must be the same and also that dimension of the gears 64 and 88 must be identical. It may be seen that by thus proportiomng the dimensions of these gears that gear 64 and gear 88 rotate at exactly the same speed to maintain a xed relation with each other until the gear 64 is moved in an axial direction on the shaft. The rotating raster or lter I6 is made up of plates 82, 84, 86 and 88. These plates have spacers 98, 92 and 94 therebetween to permit the adjustment of their position relative to each other. The tube 'I4 is connected directly to the plate 82 while the shaft 58 through spline 62 is connected to plate 88 of the raster. As the angular position of 82 is changed relative to 88 the plates 84 and 86 fan out so as to change the relationship of the openings between the disks. In one extreme position the segments 96, 98, |88 and |82 are all aligned with each other so that during approximately 75 per cent of the rotation of the assembly rays are permitted to pass through the filter and during the other 25 per cent of the time the rays are blocked by this segment. In the other extreme position the segments 86, 88, |88, |82 are fanned out with regard to each other so that the assembly I6 is a solid disk as far as the rays are concerned and no energy may be transmitted through the filter. It may thus be seen that as the disk 82 is moved relative to the disk 88 the amount of transmission may be adjusted from Athe zero to 75 per cent of the total transmission.

This adjustment is automatically made by the energization of motor 24 through the control unit 26. The motor 24 is connected through a small spur gear |84 to a much larger spur gear |86 carried concentric with the shaft 58. Also mounted concentric to the shaft 58 is the tubular section |88 of the carrier 66. This tubular section has threads I |8 of the desired lead angle cut thereon. The spur gear |86 has a mating female thread portion. The spur gear or nut |86 is prevented from axial movement by a collar member I2. It may thus be seen that as the motor 24 turns the spur gear |86, through gear |84, the carrier 66 is raised or lowered depending upon the direction of rotation of the motor. As the carrier 66 is raised or lowered it moves spiral gear -64 axially. As this gear is raised or lowered, the gear 68 is rotated relative to the shaft 58 an amount dependent upon the lead angle of the spiral gear. It may thus readily be seen that as the motor 24 causes the raising or lowering of the gear 64 with its attendant rotation of the gear 68, that the an- 'guiar' position of the disk 02 with respect to disk very high speed causing this assembly to act as a neutral lter. Second, the motor 40, through gear box 48 and crank 42, drives the entire assembly including the cell I8 in a reciprocating motion so that the test specimen 20 and the standard 22 are alternately placed over the slit in the spectrograph I0. By this action the radiation receiver I2 rst receives energy through the specimen 20 and then through specimen 22 plus the lter I6. Third,` if the energy received through each of these systems is not identical an alternating voltage is produced by the radiation receiver I2. This voltage is amplified and converted into a control voltage by a control unit 26 so as to energize the control motor 24. The control motor 24 through the mechanical system mentioned above, adjusts the position of the segments 06, 98, and |02 so that the energy transmitted through the combined filter and one specimen is identical to that transmitted through the other specimen. When this occurs the energy received by the radiation receiver I2 is the same regardless of the position of the cell I8.

If desirable, the motor 24 may be caused to drive an indicator or recorder of the standard type 200 through a separate gear train. Inthis way the transmission coeicient of the filter and thereby the difference of transmission between the unknown and standard specimen may be directly determined and/or recorded.

The entire assembly described above is mount.. ed on a plate I|4 which plate is fastened rigidly relative to the slit l0 in the analyzer.

Referring to Figures '7 and 8, details are shown of one method of mounting a standard specimen of known transmission characteristics, and a test specimen, the characteristics of which it is dcsired to determine. It may be well to here note that the specimen, whether standard or unknown, having the lower coeiiicient of energy transmission is in the position, here shown as |I8, While the other specimen having the greater coefcient of transmission is always mounted in position shown as II6. These specimens `are placed in a container and held in place on a slide 50 by means of a retaining plate |22. In one specific analysis to which this invention has been applied, the standard specimen was rock salt and this specimen was mounted in the position shown in Figures 7 and 8, as Il6. It is, or" course, within the ordinary application of applicants' invention to change various details and use various standard specimens without departing therefrom.

Referring to Figure 9, the modification of the applicants invention as here illustrated makes it unnecessary to drive the rotating lter and the specimens under test with a reciprocating motion. In this modification the slit I0 in the analyzer is covered by a mask |24 which is driven in a reciprocating motion axially to the rotating filter I6. The cell, here shown as |26, contains specimens |28 and |30, one of which has known transmission characteristics. In this modication the rotating lter I6 at all times masks the specimen |30 and the energy is directed alternately through specimens |28 and |30 by means of the reciprocation of the mask |24 having therein a window |32. It may thus be seen that energy, by the oscillation of window |32, is rst transmitted through one specimen and then the other. This modication has the advantage of reducing the reciprocating mass and thus reducing vibration.

Referring to Figure 10, a modification of the applicants invention is illustrated with a stationary analyzer slit |34 and rotating lter I6.

In this modification the rectangular cell is divided into triangular compartments |36 and |38. This cell is driven with a reciprocating motion tangential to the rotating filter. It may thus be seen that as the cell is moved tangential to the filter the energy is first transmitted through the specimen |36 and then through the specimen |38 plus the iilter |6.

Another modication of the present invention having no parts moving with a reciprocatory motion is illustrated in Figures 11, 12 and 13. This modification is the preferred form of the present invention. The rotary shutter |40 in this modication replaces the reciprocating motion necessary in the other modifications to transfer energy rst through one specimen and then through the other. The shutter |40 has a solid web |42 connected at points |44, |46, |48, |50 and |52 to an inner solid disklike center portion |54. This outer solid portion |42 is so designed that its radial dimension is always constant. This shutter is mounted concentric with the rotating filter I6 but is rotated at a much lower speed than this llter. This shutter transfers the beam of energy from one specimen to the other at a rate of ve cycles per revolution. It is, therefore, necessary to rotate the shutter at only a very low speed to obtain an output frequency that is convenient to lter and convert into a control voltage. In this modication the shutter is driven by a motor |56 through a shaft |58 and spur gears |60 and |62. In this modification the specimen is mounted in a container |64 having compartments |66 land |68. As the shutter |40 rotates, the specimens |65 and |68 are alternately exposed to the transmission of energy. This energy is, of course. focused on the specimen in the same manner as previously described and the slit I0 as previously described permits the transmission of energy into the spectrograph.

The operation of the device above described is as follows:

Referring to Figures 1 and 2, the energy is transmitted from a radiating lament or ribbon 2 through a lens system 6 onto the cell I8. This energy is projected through one specimen of lower light transmission and then through the other specimen plus the filter alternately at the frequency desired for the operation of the control unit 26. This alternate projection is accomplished in Figures 4, V5 and 6 by means of the reciprocation of the filter and specimens. It is accomplished in Figure 9 by the reciprocation of .a mask |24.

In Figure 10 this alternate projection of energy is accomplished by the tangential oscillation of the container holding specimens |36 and |38. In Figures 11, 12 and 13, the preferred form of this invention, the alternate transmission of light is accomplished by means of a rotating shutter or disk |40 having a special external configuration and specially cut openings |10. The energy, after being transmitted through the two specimens a1- ternately, is focussed on a radiation receiver I2. The output of this radiation receiver is then transmitted to the control unit 26 where it is transformed into a control voltage. This control voltage causes the actuation of the motor 24 so that it properly adjusts the filter disks, 82 through 88. In the operation of this device it is desirable to start the test with the filter in the fully closed position. The ratio of light transmission between the known and unknown specimen may be readily determined and hence the absolute energy transmission characteristics may be determined by the position of the disks of the filter under balanced condition. It is desirable that a standard type recording instrument. for example 200, be attached to this filter system preferably by means of spur gear |04 or |06 in order that the determination and recording of the transmission characteristics of the material will be fully automatic.

The present invention is considered equally applicable to the measuring of reflection characteristics throughout the infrared to ultraviolet frequency band. The same equipment may be used for both transmission and reflection measurements with the exception that the optical system must be modified as shown in Figure 3. With the optical system so modified. cell 36 with speci- 'mens 32 and 34 are oscillated in synchronism and the amount of reflective energy is received by the radiation receiver I2 and used to control the filter 40 in the same way it is used to control filter I6 described above.

Having thus described the present invention, it is obvious that various modifications Within the knowledge of workers in the art may be utilized without departing therefrom.

It is to be understood also that although the invention has been described with specic reference to a particular embodiment thereof, it is not to be so limited, since changes and alterations therein may be made which are within the full intended scope of this invention as defined by the appended claims.

We claim:

1. In apparatus for comparing the radiant energy transmission characteristics of two Specimens having different energy transmission characteristics, including a source of energy, an adjustable neutral filter consisting of a series of overlapping rotating disc sectors the magnitude of overlap of which is adjustable, placed between said source of energy and the one of the specimens having the greater radiant energy transmission characteristic, means for reciprocating specimens and associated filter so as to cause the radiant energy from said source to be focused alternately through the specimen having the lesser radiant energy transmission characteristic and through the specimen having the greater energy transmission characteristic plus said filter, an energy receiving means capable of transforming radiant energy into an electrical signal, means for focusing said energy from the specimen in the radiant energy path on to said energy receiving means, and electrical indicating means connected to the energy receiving means for determining the change in amplitude of said electrical signal as the energy is transmitted alternately through said specimens.

2. In apparatus for comparing the radiant energy transmission characteristics of two specimens having diiferent radiant energy transmission characteristics inluding, a source of energy. an adjustable neutral filter consisting of a series of overlapping rotating disc sectors the magnitude of overlap of which is adjustable, placed between said source of energy and the one of the specimens having the greater radiant energy transmission characteristic, means for reciprocating specimens and associated filter so as to cause the radiant energy from said source to be focused alternately through the specimen having the lesser radiant energy transmission characteristic and through the specimen having the greater energy transmission characteristic plus said filter, an energy receiving means capable of transforming radiant energy into an electrical signal, means for focusing said energy from the specimen in the radiant energy path on to said energy receiving means, means for automatically adjusting the overlap of the disc sectors of said filter responsive to the change in amplitude of said electrical signal so that equal radiant energy is transmitted through both specimens.

3. In apparatus for comparing the radiant energy transmission characteristics of two specimens having different radiant energy transmission characteristics including a source of energy, an adjustable neutral filter consisting of a series of overlapping rotating disc sectors the magnitude of overlap of Which is adjustable, placed Vbetween said source of energy and the one of the specimens having the greater radiant energy transmission characteristic, means for reciprocating specimens and associated filter so as to cause the radiant energy from said source to be focused alternately through the specimen having the lesser radiant energy transmission characteristic and through the specimen having the greater radiant energy transmission characteristic plus said filter, an energy receiving means capable of transforming radiant energy into an electrical signal, means for focusing said energy from the specimen in the radiant energy path on to said energy receiving means, an electrical motor connected to said filter and capable of causing adjustment thereof by adjusting the overlap of said disc sectors, a control circuit connected to the output terminals of said energy receiver so as to receive an electrical signal therefrom and produce a control voltage capable of energizing said electrical motor to cause said motor to actuate the filter and thereby cause adjustment of the disc sector overlap thereof so that equal amounts of radiant energy are transmitted through said specimens.

4. In apparatus for comparing the radiant energy transmission characteristics of two specimens as claimed in claim 3, with means for indicating the degree of energy transmission permitted by said adjustable filter.

5. In apparatus for comparing radiant energy transmission characteristics as claimed in claim 3, with means for recording the degree of energy transmission permitted by said adjustable filter and thereby recording the ratio of the energy transmission characteristics of said specimens.

6. In apparatus for comparing the radiant energy transmission characteristics of two specimens having difierent radiant energy transmission characteristics including, a source of energy, an adjustable neutral filter placed between said source of energy and the one of the specimens having the greater radiant energy transmission characteristic, means for reciprocating the specimens and associated lter so as to cause the radiant energy from the said source to be focused alternately through the specimen having the lesser radiant energy transmission characteristic and through the specimen having the greater energy transmission characteristic plus said filter, an energy receiving means capable of transforming radiant energy into an electrical signal, means for focusing said energy from the specimen in the radiant energy path on to said energy receiving means, and means for automatically adjusting said filter responsive to the change in amplitude of said electrical signal so that equal radiant energy is transmitted through both specimens.

7. In apparatus for comparing the radiant energy transmission characteristics of two specimens having diierent radiant energy transmission characteristics including, a source of energy, an adjustable neutral lter consisting of a series of overlapping rotating disc sectors the magnitude of overlap of which is adjustable, placed between said source of energy and the one of the specimens having the greater radiant energy transmission characteristic, means for reciprocating said specimens and associated lter so as to cause the radiant energy from said source to be focused alternately through the specimen having the lesser radiant energy transmission characteristic and then through the specimen having the greater energy transmission characteristic plus said filter, an energy receiving means capable of transforming radiant energy into an electrical signal, means for focusing said energy from the specimen in the radiant energy path on to said energy receiving means, and means for adjusting the overlap of the disc sectors of said iilter responsive to the change in amplitude of said electrical signal so that equal radiant energy is transmitted through both specimens.

EDWARD JOHN MARTIN. ROBERT N. FRAWLEY.

REFERENCE S CIT ED The following references are of record in the iile of this patent:

UNITED STATES PATENTS 

